The field of this invention relates to an apparatus for supporting and maintaining together fractured bone sections of the femur in the normal position to assist in proper healing.
The femur, at the hip, terminates at a femoral head. Connecting the femoral head to the main portion of the femur is a femoral neck. The head constitutes an enlarged ball shaped bone tissue, while the femoral neck is a smaller diametered cylindrical shaped bone tissue. The femoral head is composed of spongy tissue while the femoral neck is composed of hard bone tissue similar to the main body of the femur.
Fractures of the femur, particularly across the femoral neck, are rather common. It was determined quite early that the setting of such fractures by using casts, was not likely to be very successful, due to movement of the hip joint. It was quickly determined that some means would be required for internal fixation of the proximal end of the femur.
Initially attempts were made at internal fixation through the use of either a round or a polygonal shaped nail. However, this type of nail was quickly abandoned because it brought about only partial and temporary fixation. Then in the late 20's, it was discovered that good fixation could be achieved by using a flanged nail. This type of nail came to be known as the Smith-Petersen Nail, named after its inventor.
Soon after the development of the Smith-Petersen nail, it was determined that even a better fixation of the fracture could be achieved by attaching a plate to the lateral side of the shaft of the femur. One good use of such a plate would be to prevent the nail in time from working itself out of position. Usually such nails are required to remain in position for extended periods of time, such as three to six months. However, usage of such a plate has several disadvantages such as destroying additional bone tissue in attaching of the plate to the femur, significantly increasing the equipment which the patient must tolerate over an extended length of time, significantly complicates the attachment at the back end of the nail, and such plates do not allow the patient to be mobilized as soon as the patient should. The results of a patient remaining too long in a sedimentary position are well known for those in the medial profession. Sedimentation is particularily hazardous for geriatrics, the group of persons most likely to incur fractures of the femur, because geriatrics readily contract pneumonia, respiratory problems, heart problems, ulcers, or generalized weakness when subjected to inactivity.
Although the Smith-Petersen nail significantly enhanced the fixation of the femur, a high percent of postoperative complications still arise. The most important complications are:
1. The fracture will not unite in about ten percent of the cases, and
2. The femoral head becomes necrotic and fragmentates (referred to as capital necrosis) in about thirty to forty percent of the cases.
It is now generally assumed that capital (necrosis) is due to vascular injuries. As the tip of the Smith-Petersen nail penetrates the femoral head, a significant amount of area of the tissue within the femoral head is destroyed. It is believed that this destroying of the tissue produces the capital necrosis since the nail causes significant damage to the blood supply to the femoral head. When capital necrosis does occur, it is necessary to re-operate on the patient, remove the femoral head, and insert a metallic prosthesis.
The problem with the fracture not uniting, is believed to be due to poor fixation of the femoral head to the femur. This is an indication that the Smith-Petersen nail is not entirely satisfactory.